The production and release of catecholamines by the kidney are being studied in the anesthtized dog. We are using simultaneous sampling from the aorta, renal veins, and ureters. This is done in conjunction with measurements of arterial blood pressure, renal blood flow and glomerular filtration rate to allow for an overall assessment of these physiologic interactions. the effect of an acute reduction in renal blood flow to one kidney on the above parameters is also being evaluated.